docs: def _find_cf_standard_name_table(self, ds):
          '''
          Parse out the `standard_name_vocabulary` attribute and download that
          version of the cf standard name table.  If the standard name table has
          already been downloaded, use the cached version.  Modifies `_std_names`
          attribute to store standard names.  Returns True if the file exists and
          False if it fails to download.
  
          :param netCDF4.Dataset ds: An open netCDF dataset
          :rtype: bool
          '''
          # Get the standard name vocab
          standard_name_vocabulary = getattr(ds, 'standard_name_vocabulary', '')
  
          # Try to parse this attribute to get version
          version = None
          try:
              if 'cf standard name table' in standard_name_vocabulary.lower():
                  version = [s.strip('(').strip(')').strip('v').strip(',') for s in standard_name_vocabulary.split()]
                  # This assumes that table version number won't start with 0.
                  version = [s for s in version if s.isdigit() and len(s) <= 2 and not s.startswith('0')]
                  if len(version) > 1:
                      return False
                  else:
                      version = version[0]
              else:
                  # Can't parse the attribute, use the packaged version
                  return False
          # usually raised from .lower() with an incompatible (non-string)
          # data type
          except AttributeError:
              warn("Cannot convert standard name table to lowercase.  This can "
                   "occur if a non-string standard_name_vocabulary global "
                   "attribute is supplied")
              return False
  
          if version.startswith('v'):  # i.e 'v34' -> '34' drop the v
              version = version[1:]
  
          # If the packaged version is what we're after, then we're good
          if version == self._std_names._version:
              print("Using packaged standard name table v{0}".format(version), file=sys.stderr)
              return False
  
          # Try to download the version specified
          try:
              data_directory = util.create_cached_data_dir()
              location = os.path.join(data_directory, 'cf-standard-name-table-test-{0}.xml'.format(version))
              # Did we already download this before?
              if not os.path.isfile(location):
                  util.download_cf_standard_name_table(version, location)
                  print("Using downloaded standard name table v{0}".format(version), file=sys.stderr)
              else:
                  print("Using cached standard name table v{0} from {1}".format(version, location), file=sys.stderr)
  
              self._std_names = util.StandardNameTable(location)
              return True
          except Exception as e:
              # There was an error downloading the CF table. That's ok, we'll just use the packaged version
              warn("Problem fetching standard name table:\n{0}\n"
                   "Using packaged v{1}".format(e, self._std_names._version))
              return False